High Field Mössbauer Studies of Multiferroic
Ba0.5Sr1.5Zn2Fe12O22 Hexaferrite
N.Raju1 , S.Shravan Kumar Reddy1, Ch.Gopal Reddy1, P.Yadagiri Reddy1#, K.Rama Reddy1
and V.Raghavendra Reddy2
1
Department of Physics, Osmania University, Hyderabad, India
2
UGC-DAE CSR, Khandwa Road, Indore – 452 001, India
# Corresponding author e-mail: yadagirireddy@yahoo.com
Abstract:
Magnetic studies of polycrystalline
Ba0.5Sr1.5Zn2Fe12O22 multiferroic Y-type hexaferrite reveal
that the appeared field induced transitions in the M-H curve
are similar to the single crystal behaviour. From infield
Mössbauer studies it can be said that the occupancy of Fe+3
ions in the tetrahedral is more than the octahedral sites by
doping the Sr at Ba site.
Keywords: Multiferroics; Cation Distribution; Mössbauer
Resonance; Field induced transitions; Hexaferrite.
occupation in tetrahedral and octahedral sites are
changing and reduction of intensity peaks suggests the
spin tilting in the c-plane of hexaferrite.
Conclusions: From magnetisation studies it is observed that the pollycyrstaline samples are showing
similar behaviour to single crystals. From the infield
Mössbauer spectra the occupation of Fe +3 ions at tetrahedral sites is more than the Sr free sample. The
doping of the Sr ion in the place of Ba ion produces
the more occupation of Fe+3 ions in tetrahedral sites.
Introduction:
Ba0.5Sr1.5Zn2Fe12O22
Ba0.5 Sr1.5 Zn 2Fe12O 22
M(emu/gr)
10
300K
300k
(a)
0
-10
0
2000
Magnetic field(Oe)
0
(b)
Ba0.5Sr1.5Zn2Fe12O22
30
-20
ZFC
FC
97k
25
Magnetization(emu/g)
M(emu/gr)
20
20
15
319K
10
5
Inpresence of 500 Oe field
0
0
100
200
300
400
Magnetic Field(Oe)
-20000
0
20000
Magnetic field(Oe)
Figure 1: Magnetisation studies of BSZFO (a) Field
induced transitions at 300K (b) FC and ZFC Curve in
presence of 500 Oe.
5K
Transmission (arb.units)
The Ba0.5Sr1.5Zn2Fe12O22 (BSZFO) system is a Y-type
hexaferrite reported as a multiferroic material below
110K [1]. The fundamental crystal structure of this
system belongs to the R3m space group with hexagonal structure. The magnetic structure of the system
consists of spin blocks S [Me2+Fe4O8 where Me is
divalent metal ion] and T [(Ba,Sr)2 Fe8O14 ] along the
C axis. In these spin blocks the Fe+3 ions are occupied
the tetrahedral (6cIV, 6cIV*) and octahedral (18hVI, 6cVI,
3aVI, 3bVI) sites. The unit cell of the Y-type hexaferrites composed with three structurally equivalent
(T1/2ST1/2)
blocks along the c- axis. In each
(T1/2ST1/2) block Fe spins are bunched in the form of
collinear ferrimagnet and the spin rorates in the cplane with an angle Фo which is responsible for multiferroic behaviour [1-3].
Experimental: The BSZFO polycrystalline samples
are prepared through conventional solid state reaction
method. The XRD, magnetization and infield Mössbauer studies are carried out on these samples.
Results: The magnetic studies of BSZFO shown in
Figure 1. The M-H loop was obtained from 0 to 2T
external magnetic field at 300K. The hysteresis curve
showing the sharp bends [ inset (a) , which is magnified version of M-H curve from 0 to 0.3T ] are represents the field induced magnetic transitions in the material which is similar to the single crystal behaviour
[1]. In the ZFC and FC curves [ inset (b) ] of BSZFO
from 5K-350K temperatures we have observed the
AFM transition at 319K which is nearer to the single
crystal transition value, TN. The Mössbauer specta at
5K by applying the external magnetic fields (0T, 1T,
2T, 3T, 4T and 5T) are shown in Figure 2. The observed spectra are fitted by assuming two sites S1:
Tetrahedral (6cIV, 6cIV*) and S2: Octahedral (18hVI,
6cVI, 3aVI, 3bVI) for confident fit. From infield Mössbauer spectra it is clearly observed that the Fe+3 ions
-15
-10
-5
0
5
10
15
-5
0
5
10
15
-5
0
5
10
15
-5
0
5
10
15
-5
0
5
10
15
-5
0
5
10
15
5K, 1Tesla
-15
-10
5K, 2Tesla
-15
-10
5K, 3Tesla
-15
-10
5K, 4Tesla
-15
-10
5K, 5Tesla
-15
-10
Velocity (mm/s)
Figure 2: Mössbauer spectra of BSZFO at 5K in presence of 0 to5T external magnetic fields.
References:
[1]. T.Kimura, G.Lawes, A.P Ramirez, Phy.Rev.Lett.
94,137201 (2005)
[2]. N Momozawa et al, J. Phys. Soc. Jap. 54,
3895(1985)
[3]. N Momozawa, and Y.Yamaguchi, J. Phys. Soc.
Jap. 62, 1292 (1993)